A properly installed clutch and brake master cylinder will save you time, many headaches, and possibly even your life. For some, staring at a master cylinder kit before it is assembled can be rather intimidating; fear not though, because the process is much more straightforward than you would imagine. Tilton Engineering understands how daunting the process can look to the average enthusiast, which led them to release a video explaining the process of assembling one of their master cylinders, using their 76-series for reference.
The first step before beginning the actual assembly process is to confirm that the bolts or studs that mount the master cylinder to the pedal assembly are the correct length. Too short and the threads won’t fully engage, leading to a quick failure when put under stress, too long and it may not clear the inlet port on the master cylinder, possibly damaging the body. Once this has been confirmed, you are ready to begin the install.
Mounting And Pushrod Geometry When mounting the master cylinder to the assembly, it is very important to make sure that the angle of the pushrod is within three degrees of the bore throughout its entire stroke. Otherwise, the angle may interfere with the full range of the pedal throw or damage the master cylinder due to the excess stress being placed on the rod.
To adjust the amount of angle on the pushrod, it’s as simple as shortening the rod by rotating its body, or extending it either by rotating it or swapping it out for a longer piece of all thread. Be sure to eliminate any preload on the pushrod to allow the hydraulic fluid to fully bleed back into the reservoir when the pedal is at rest.
Left: Displaying a master cylinder with an angle on the pushrod. | Right: Pushrod ready for adjustment. Be sure to tighten the locking nut on the pushrod when you have finished setting it.
It’s also important to note that the spring built into the Tilton master cylinder is designed to return the piston and pushrod to its fully relaxed state, when using other pedal designs the pushrod may need the assistance of an external return spring for the brake and clutch.
Fitting Your Fittings The type of fitting material that can be safely used will vary depending on if you’re plumbing a brake or clutch master cylinder.
If assembling a brake MC it is required to use steel fittings on the high pressure outlet ports, due to the amount of pressure the hydraulic fluid is being exposed to in comparison to a clutch. Aluminum fittings may be used on any of the inlet ports on the brake MC and even on the outlet fittings for clutches.
Left: Brake master cylinder with steel outlet fitting/plug and an aluminum inlet fitting. | Right: A pair of clutch master cylinders using only aluminum fittings.
Remember, AN fittings are designed to be self sealing and have a 37 degree flare on the male end and an inverted 37 degree flare on the female fitting. Never use thread sealant or teflon tape on AN fittings unless you want to compromise the seal and leak fluid, if a fitting is still leaking after being reinstalled and properly torqued it will need to be replaced.
All of Tilton’s master cylinders are tapped for -AN3 outlet ports, except for the 73-series which uses an eighth inch NPT port. The 76-series featured in this video includes two high pressure outlet ports, with the outlet on top of the body being designed for use with deeper banjo fittings.
Letting Gravity Do The Work To increase braking consistency and to prevent any air from being easily trapped in the system, make sure that the remote reservoir (if equipped) is mounted at a point that is above the master cylinder. This will allow the DOT-3 or DOT-4 fluid in the reservoir to gravity feed into the cylinder, making the bleeding process much more reliable.
Try your best to make sure that the high pressure lines from the cylinder follow a downward grade as often as possible, and avoid any loops or high spots to prevent air from becomming trapped, and making the system much more simple for quick trackside bleeding.
Additional Precautions If installing a brake master cylinder on a vehicle equipped with an anti-lock braking system (ABS), the pressure pulses produced when the ABS system is activated are likely to damage the internal seals of most aftermarket master cylinders, except for units like Tilton’s ABS compatible 74-series master cylinder.